High frequency electric discharge devices



March 9, 1965 J. E. BAKER 3,173,054

HIGH FREQUENCY ELECTRIC DISCHARGE DEVICES Filed- March 7, 1961 2Sheets-Sheet 1 my 0R (AH/V Mul an-R 1y f 42%, am: 1 1

March 9, 1965 Filed March 7, 1961 J. E. BAKER 3,173,054

HIGH FREQUENCY ELECTRIC DISCHARGE DEVICES 2 Sheets-Sheet 2 Fig. 2

I N VEN FUR ANN 6WM/ 319M571 BY- 40414, am. 15

United States Patent 3,173,054 HIGH FREQUENCY ELECTRIC DISCHARGE DEVICESJohn Edwin Baker, Walthamstow, London, England, as-

signor to The M-() Valve Company Limited, London, England Filed Mar. 7,1961, Ser. No. 93,894 Claims priority, application Great Britain, Mar.10, 1960, 8,567 60 4 Claims. (Cl. SIS-39.53)

This invention relates to high frequency electric discharge devices ofthe kind having a high frequency connector in the form of a pair ofcoaxial conductors the inner of which is sealed through a member ofelectrically insulating material which forms part of the envelope of thedevice.

It is sometimes desirable to couple such a connector to an externalfeeder in the form of a coaxial line. If in such a case the ends ofconductors of the coaxial line are directly coupled in operation to theconductors of the relevant high frequency connector, there may be a riskof damage to the seal of the inner conductor of the connector, forexample, due to vibration of the coaxial line. Such damage is especiallyliable to occur with high power devices where it is desirable that theline should be of rigid construction.

It is an object of the present invention to provide a high frequencyelectric discharge device of the kind specified, in which the connectormay be coupled to a feeder in the form of a coaxial line withoutincurring the above mentioned risk.

According to the invention, a high frequency electric discharge deviceof the kind specified has associated with it a cavity resonator situatedexternal to the envelope of the device and rigidly fixed with respect tothe envelope with a part of the wall of the resonator adjacent the sealof the inner conductor of the connector, the wall of the resonator beingelectrically coupled to the outer conductor of the connector, the innerconductor of the connector extending into the resonator through anaperture in said part of the wall of the resonator, and the resonatorbeing provided with means for coupling to it one end of an externalfeeder in the form of a coaxial line.

One arrangement in accordance with the invention will now be described,by way of example, with reference to the accompanying drawings in which:

FIGURE 1 is a part-sectional side elevation of a vane type magnetronemploying double ring strapping; and

FIGURE 2 is a sectional elevation along the line II-Il in FIGURE 1;

Referring to the drawings, the electrode structure of the magnetron ishoused within a sealed metal envelope 1 comprising a number of coaxialtubular portions of dillerent diameters arranged end to end, the portion2 of the largest diameter constituting part of the anode of themagnetron.

The anode further includes eight vanes 3, each of which is in the formof a thin rectangular metal plate, the vanes 3 being housed within theportion 2 and being symmetrically disposed around the axis of the magnetron, in planes containing the axis of the magnetron, with their loner edges parallel to the axis of the magnetron. At their outer longeredges the vanes 3 fit in slots formed in the inner surface of theportion 2 and the inner longer edges of the vanes 3 lie adjacent acylindrical cathode 4 housed coaxially within the anode.

The vanes 3 are strapped together by means of two metal rings 5 and 6 ofdifferent diameters disposed coaxially within the portion 2 in a planesubstantially coincident with one set of shorter edges of the vanes 3,

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slots 7 being cut in the vanes 3 so that each ring 5 or 6 connectstogether a different set of alternate ones of the vanes 3. The vanes 3are similarly strapped together by means of two similar rings (notvisible in the drawings) disposed coaxially within the portion 2 in aplane substantially coincident with the other set of shorter edges ofthe vanes 3, but here the larger ring connects together the vanes whichat the other end of the anode are connected together by the smaller ring6 and vice versa.

Power is extracted from the magnetron via an output connector 8 in theform of a pair of coaxial conductors extending radially from the anodeof the magnetron. The outer conductor of the connector 8 is constitutedpartly by a substantially frustro-conical copper block 9 and partly by ashort length of copper tubing 10, the block 9 being brazed at itsnarrower end to the portion 2 and having an axial aperture 11 extendinginto it from its smaller face which communicates with a correspondingaperture 12 in the wall of the portion 2. The tubing 10 is sealedcoaxially into an aperture 13 which extends axially into the block 9from its larger face and which communicates at about the centre of theblock 9 with the aperture 11, the aperture 13 being of larger diameterthan the aperture 11. At its end remote from the anode, the tubing 10opens into a short portion 14 of larger diameter than the portion sealedinto the aperture 13, and into this portion 14 is sealed a ceramic disc15; the block 9, the tubing 10 and the disc 15 thus all form part of theenvelope 1 of the magnetron. The inner conductor of the connector 8is'constituted by a. copper conductor 16 which is secured at one end tothe strapping ring 5, passes axially through the apertures 11, 12 and 13and the tubing 10, passes through a seal in the disc 15 and terminatesin a probe 17.

The magnetron is secured to a metal block 18, described below in greaterdetail, by means of bolts 19 which pass through holes provided in aflange 20 at the wider end of the block 9 and through correspondingholes in a flange 21 provided at the end of the portion 14 of the tubing10, the flange 21 being trapped between the block 18 and tubular spacers22, the spacers 22 serving to hold the block 9 away from the block 18.

The magnetic field required for operation of the magnetron is providedby a permanent magnet constituted by a tubular member 23 having alongitudinally extending slit; a pair of fiat rings 24 which fitrespectively in contact with the ends of the tubular member 23 and apair of hollow substantially frustro-conical members 25 which fitcoaxially within the tubular member 23. The magnet is disposed with thetubular member 23 coaxially surrounding the magnetron and the narrowerends of the members 25 locating on coaxial portions 26 of the envelope 1adjacent the portion 2 in which are housed pole pieces for the magnet(not visible in the drawings). The slit in the member 23 is positionedso as to accommodate the block 9 which itself is partly cut away toenable it to fit in the slit.

The magnetron and magnet assembly are housed within a protective casing27 which is secured to the block 18, leads (not visible in the drawings)to the electrodes of the magnetron being brought out through an opening28 in the casing 27. The space within the casing 27 not occupied by themagnetron and the magnet assembly is filled with silicone rubber 29, therubber 29 being injected into the casing 27 in a liquid state via theopening 28 which is plugged with thermosetting resin loaded with silicaflour 30 when the rubber 29 has hardened.

The block 18 has formed in it a rectangular cavity 31 of dimensions suchas to be resonant approximately at the frequency of the oscillationproduced by the magnetron. The probe 17 extends into the cavity 31 via acircular aperture 32 formed in the wall of the cavity 31 adjacent theceramic disc 15, and a similar aperture 33 is formed in the oppositewall of the cavity 31, the aperture 33 being coaxially surrounded by'acircular choke slot arrangement 34 formed in the face of the block 18,the slot being filled with a suitable dielectric material. The cavity 31is tunable by means of a slug 35 which screws into a tapped aperture ina side wall of the cavity 31.

In operation of the magnetron, power from the magnetron is fed to thecavity 31 via the connector 8 and power may be supplied from the cavity31 to a load via an external coaxial line (not shown) whose outerconductor is secured to the main face of the block 18 remote from themagnetron, and whose inner conductor terminates in a probe which extendsinto the cavity 31 via the aperture 33. Clearly, there is little risk ofvibration causing damage to the seal via which the inner conductor ofthe connector 8 passes through the envelope 1. In addition, the cavity31 acts as a tuned transformer which enables impedance matching betweenthe load and the magnetron to be obtained.

In the arrangement described above, by way of example, the dischargedevice has only one high frequency connector and has associated with itonly one cavity resonator. In other arrangements in accordance with theinvention, for example, where the discharge device is an amplifyingdevice, the discharge device may have more than one high frequencyconnector and have associated with it more than one cavity resonator.

I claim:

1. In combination, for use with an external feeder in the form of acoaxial line:

a high frequency electric discharge device having a sealed envelope andhaving a high frequency connector in the form of a pair of coaxialconductors, the outer conductor being constituted by a generally tubularrigid metallic member which projects outwardly from the main body of theenvelope and itself forms part of the envelope and the inner conductorbeing sealed through a member of insulating material which is sealedacross the interior of the outer conductor adjacent its outer end andwhich also forms part of the envelope, the inner conductor having aportion projecting beyond the outer end of the outer conductor;

a cavity resonator situated external to the envelope of the device, theresonator having an aperture in its wall;

means rigidly clamping said outer conductor to the wall of the resonatorwith the outer end of the outer conductor in contact with the exteriorof the wall of the resonator around said aperture and with said portionof the inner conductor extending into the resonator through saidaperture;

and means for coupling the resonator to one end of said external feeder.

2. The combination according to claim 1, in which the discharge deviceand said clamping means are disposed within a rigid housing which ispartly constituted by a portion of the wall of the resonator, theremaining space within the housing being substantially filled with aresilient packing material.

3. The combination according to claim 1, including means to vary theresonant frequency of the resonator.

4. In combination, for use with an external feeder in the form of acoaxial line:

a high frequency electric discharge device having a sealed envelope andhaving a high frequency connector in the form of a pair of coaxialconductors, the outer conductor being constituted by a generally tubularrigid metallic member which projects outwardly from the main body of theenvelope and itself forms parts of the envelope and the inner conductorbeing sealed through a member of insulating material which is sealedacross the interior of the outer conductor adjacent its outer end andwhich also forms part of the envelope, the inner conductor having aportion projecting beyond the outer end of the outer conductor, and theouter conductor having an outwardly extending flange at its outer end;

a cavity resonator situated external to the envelope of the device, theresonator having an aperture in its wall;

means rigidly clamping said outer conductor to the wall of the resonatorwith said flange in contact with the exterior of the wall of theresonator around said aperture and with said portion of the innerconductor extending into the resonator through said aperture;

a rigid housing which is partly constituted by a portion of the wall ofthe resonator and within which the discharge device and said clampingmeans are disposed, the remaining space within the housing beingsubstantially filled with a resilient packing material;

and means for coupling the resonator to one end of said external feeder.

References Cited by the Examiner UNITED STATES PATENTS 2,283,895 5/42Mouromtseif et al. 333-83 X 2,603,711 7/52 Woodyard 33383 2,657,31410/53 Kleen et al. 315-393 X 2,820,127 1/58 Argento et al 333-83 X DAVIDJ. GALVIN, Primary Examin r.

ARTHUR GAUSS, GEORGE N. WESTBY, Examiners.

1. IN COMBINATION, FOR USE WITH AN EXTERNAL FEEDER IN THE FORM OF ACOAXIAL LINE: A HIGH FREQUENCY ELECTRIC DISCHARGE DEVICE HAVING A SEALEDENVELOPE AND HAVING A HIGH FREQUENCY CONNECTOR IN THE FORM OF A PAIR OFCOAXIAL CONDUCTORS, THE OUTER CONDUCTOR BEING CONSTITUTED BY A GENERALLYTUBULAR RIGID METALLIC MEMBER WHICH PROJECTS OUTWARDLY FROM THE MAINBODY OF THE ENVELOPE AND ITSELF FORMS PART OF THE ENVELOPE AND THE INNERCONDUCTOR BEING SEALED THROUGH A MEMBER OF INSULATING MATERIAL WHICH ISSEALED ACROS THE INTERIOR OF THE OUTER CONDUCTOR ADJACENT ITS OUTER ENDAND WHICH ALSO FORMS PART OF THE ENVELOPE, THE INNER CONDUCTOR HAVING ANPORTION PROJECTING BEYOND THE OUTER END OF THE OUTER CONDUCTOR; A CAVITYRESONATOR SITUATED EXTERNAL TO THE ENVELOPE OF THE DEVICE, THE RESONATORHAVING AN APERTURE IN ITS WALL;